In Vincent, et al U.S. Pat. No. 4,424,649, an abrasive cutter for cutting metallurgical samples and the like includes a motor-driven, rotatable abrasive cutter wheel, a vise assembly for holding the workpiece to be cut, and a manually operable workpiece advance lever which is actuated by the operator to move the vice assembly along the path toward the cutter to bring the workpiece into engagement with the cutter wheel. Devices of this type are commercially available. For example, Buehler Ltd. of Lake Bluff, Illinois sells the Isomet Low Speed Saw, which is for the precision, low deformation cutting of metal, ceramic, and geological specimens, typically for microscopic analysis of the specimen surface. The Isomet Low Speed Saw utilizes a weight system to place a constant pressure between the saw and the sample to be cut. Such a weight system requires a manual application of weights to a spindle to achieve the desired pressure of the saw against the workpiece.
To protect the quality and integrity of the workpiece surface, and also to protect the saw blade, it is important to assure that excess torque is not applied to the saw during the cutting process. Particularly at higher rotation speeds and at higher pressures, the heat generated by the sawing process can damage either the sample, the saw blade, or both. In a gravity-type system where the pressure of the saw blade against the workpiece is governed by the number of weights applied to the system, an operator's miscalculation may cause excessive weight to be added to the system at the particular torque being applied. Also in such cutting processes, it would be desirable to operate with a predetermined saw blade rotation, but if the saw is set to operate at desired rate of rotation, that makes the possibility of overheating even more likely in the event excess weight has been accidentally used, because the overall energy placed in the system will rise as the motor forces the saw blade to cut at that set rotation rate under high friction, high torque circumstances.
In accordance with invention, apparatus is provided for processing the workpiece, for example a saw apparatus, in which the pressure between the saw and the workpiece can be automatically maintained by electronic means. This of course provides a significant advantage in ease of operation, and permits changing of the pressure between the saw blade and the workpiece as desired during the operation. Additionally, the invention permits an override system to reduce the pressure between the saw blade and workpiece when the torque approaches a preset maximum at which damage to the workpiece, the saw blade, or the saw motor might occur due to excessive torque or temperature of operation.